I didn't delete it either so it must have been the ups and downs yesterday. Lost a couple of posts myself.

Anyhow back to the fun. When they said to put it at the MAC they forgot an important part. You want to put it at or slightly ahead of the 25% chord point of the MAC.

Why you ask? Symetrical airfoils tend to be neutral to weathervaning if they are pivoted at the 25% chord point. If you put the pivot so that there's equal area ahead and behind like you may think you'll find that it wants to strongly pvot up or down rather than politely align itself with the airflow. If you put the pivot right on the 25% point the loads will pretty much balance and it won't kick around much. If it's slightly ahead like at 22 or 23% it'll show a very slight self centering action.

Although with the pivot below the surface like this it'll have some drag and that will put some very variable loads on the servo I would think.. But in the airfoil or below you want that pivot point to be at or a % or two ahead of the 25% chord of the surface's MAC.